Meridiosignum convexum, Just & Wilson, 2021

Just, Jean & Wilson, George D. F., 2021, Redescriptions and new species in the ‘ Austrosignum-Munnogonium’ complex sensu Just & Wilson (2007), mainly from the Southern Hemisphere (Crustacea Isopoda: Paramunnidae), Zootaxa 4952 (3), pp. 401-447 : 421-424

Meridiosignum convexum sp. nov.

( Figs 12–13 )

Type fixation. Holotype, ♀, NIWA 143904.—Here designated.

Type locality. Campbell Island, New Zealand.

Etymology. The species is named for the convex lateral margins of pereionites.

Material examined. Holotype. ♀, 1.7 mm, east of Vire Point , Perseverance Harbour, Campbell Island, New Zealand, 52°33’S, 169°10’E, red algae, sediment and detritus trapped in slimy mucous, J.K. Lowry, stn CA 95, 3 Jan 1980, NIWA 143904.

Paratypes. Campbell Island , New Zealand: Same data as holotype, NIWA 143905 (1 ♂, 4 ♀) . Perseverance Harbour , east side of Vire Point, 52°33’S, 169°10’E, 3 Jan 1980, AM P76910 (2 spms) . Cliffs west of Davis Point , Perseverance Harbour, Campbell Island, 52°34’S, 169°13’E, from mixed red algae from among boulders, J.K. Low- ry, 7 Feb 1980, CA–277, AM P76911 (1 young ♂, 1 ♀) . Depot Point , Tucker Cove , Perseverance Harbour, Camp- bell Island, 52°33’S, 169°7’E, from Codium , Xiphophora ; red, green and brown algae, P.C. Terrill, 31 Dec 1979, stn CA–50, AM P60457 (2 young ♂, 3 ♀) . Caves east of Divers Point , Perseverance Harbour, Campbell Island, 52°34’S, 169°11’E, from Macrocystis pyrifera holdfasts, red and coralline algae, P.C. Terrill, 3 Jan 1980, stn CA– 86, AM P76912 (1 juv. ♂) . East of Vire Point , Perseverance Harbour, Campbell Island, 52°33’S, 169°10’E, from sediment, mussels and broken shell, P.C. Terrill, 12 Feb 1980, stn CA–335, AM P76908 (1 ♂) . Depot Point , Tucker Cove , Perserverance Harbour , Campbell Island, New Zealand, 52°33’S, 169°7’E, among Codium , Xiphophora , red, green, and brown algae, low tide mark, P.C. Terrill, 31 Dec 1979, stn CA–51, AM P68207 (6 adult ♀, 3 juv.) . Depot Point , Tucker Cove , Perseverance Harbour, Campbell Island, 52°33’S, 169°7’E, from Codium , Xiphophora , red, green, and brown algae, low tide mark, P.C. Terrill, 31 Dec 1979, stn CA–54, AM P68208 (4 adult ♀, 2 young ♀, 2 ♂) . Cliffs west of East Cape , Smoothwater Bay, Campbell Island, 52°33’S, 169°13’E, 12–18 m, from holdfast of Durvillea antarctica , sediment and red algae, 13 Jan 1980, stn CA–150, AM P68209 (1 adult ♀) .

Snares Island, New Zealand: Senecio Pool , 6–7 m, among Caulerpa brownii on vertical rock, G.D. Fenwick, 6 January 1977, stn SA–3488, NMV J40707 (5 ♂, 8 ♀, 3 juv.) .

Auckland Island , New Zealand: Ranui Cove, 50°32.5’S, 166°17’E, among M. pyrifera holdfasts and red algae on anchor of “ Acheron ”, J.K. Lowry, 7 Feb 1973, stn SA–1485, AM P92211 (6 ♀, 4 juv.) . Rose Island to Shoe Island, Port Ross, 50°31’S, 166°15’E, J.K. Lowry, 14 Feb 1973, stn SA–1489, AM P92212 (1 preparatory ♀) .

Description. Body width 0.61 length in female, 0.57 length in male, widest in female at pereionite 3, widest in terminal male at pereionites 1 and 2.

Head longer in male than female, length in male 0.6 width, in female 0.5 width; length posterior to eyestalks 1.3 anterior length in male 0.93 in female. Frontal margin with angular lateral margins adjacent to antennae, shallow convex, almost straight medially. Eyestalks in female length 1.7 width, in male 2.6 width, slightly expanded distally, apex rounded, long axis angling forward at approximately 30° in female and male.

Pereionites 1–6 lateral margins not projecting, rounded; pereionite 7 lateral margins with 2 (♀) and 1 (♂) re- curved spines apically; pereionite 1 of terminal male greatly enlarged, sagittal length in terminal male 2.8 pereionite midline length, in female 2.2 pereionite midline length. Coxae 2–4 (♂) and 1–4 (♀) not visible in dorsal view; coxal plate 1 in male rounded forward pointing; coxae 5–7 visible in dorsal view, with 1 recurved spine on apex.

Pleon length 1.1 width in female, 1.2 width in male. Pleonite 1 width 0.7 of distance between uropods (♂, ♀), length 0.30 width in female, 0.25 in male. Pleotelson broadly rounded, without inflection between proximal and lateral margins, proximal margin shorter than lateral margin; proximal margin forming 50° angle with medial axis of pleon (♂, ♀); lateral margins with 10–13 denticles each side; posterior projection forming 70° angle (♂, ♀), set apart from lateral margins by concavity at level of uropods, apex broadly rounded with fringe of long setae.

Antennula articles 1–2 combined extending beyond eyestalk apex; article 1 shorter than 2, tubular, slightly broader than 2; article 3 as long as 4 and 5 combined, 5 slightly shorter than 6.

Antenna article 3 tubular, width 0.40 length, article 5 distinctly shorter than article 6; flagellum with 7 articles, proximal article as long as second and third articles combined.

Pereiopod I basis length 3.3 width, with crenate ridge on anterior margin; ischium with row of blunt spines on anterior margin; merus with several small anterodorsal spines; carpus triangular, distal width subequal to posterior margin length, posterior margin with 2 spines proximal to robust setae, 1 spine between robust setae, one spine distal to robust setae; propodus narrowing distally to insertion of dactylus, with 2 robust setae on opposing margin.

Male pleopods I lateral lobes distinctly projecting from lateral margin, width 0.30 distance to midline; distal sublobe with tuft of simple setae; distal projection length 0.32 pleopod total length, combined lobes forming acute angle of 60°, with pointed, setiferous apices. Female operculum distal part tapering with moderately concave distolateral margins, width 0.72 length, setiferous apex broadly rounded.

Uropods dorsal and directly adjacent to lateral margin of pleotelson; protopod absent or hidden.

Size. Largest female 1.7 mm; largest male 1.7 mm.

Distribution. New Zealand, subantarctic islands, intertidal to 23 m.

Remarks. Meridiosignum convexum sp. nov. is most similar to M. minidenticulata Just & Wilson, 2007 except that the pleotelson lateral margins has 10–13 large denticles whereas the latter species has 15–17 small denticles.

Figures

FIGURE 12. Meridiosignum convexum sp. nov., holotype, ♀, except M, paratype, T♂. p1–2, pereiopods I and II; up, uropod. Scale for habitus (both), 0.5 mm.

FIGURE 13. Meridiosignum convexum sp. nov., holotype, ♀, except M, paratype, T♂. a, antenna; au, antennula; cvv, head ventral view; op, operculum; pl1, pleopod I.